neume-extra

Copperbox revision 1452.

The overlay example now works for LilyPond. Unlike the example in the original Neume, I don't try to generate output in the parallelMusic form. This means I didn't need to add any new code to get overlays working.

Now that all the examples work, the two packages neume-core and neume-extra are functionally equivalent to the original Neume (only a week's work...).